1. Field of the Invention
The present invention relates to an image information processing apparatus and an image information processing system and, more particularly, to conversion of the aspect ratio of an image. In such conversion, during recording, the aspect ratio of image information to be recorded and reproduced is compressed or expanded through optical means and the resultant image having a different aspect ratio is recorded, and during reproduction, the different aspect ratio is converted into the original aspect ratio.
2. Description of the Related Art
In general, the aspect ratio of an image carried by a television video signal which is transmitted according to a conventional television system (for example, the NTSC system) is 4:3, and this 4:3 aspect ratio is widely adopted in the field of standard television systems.
In recent years, the image quality of a television signal has been further improved and the size of a screen has become larger and larger. However, since the television video signal itself still conforms to such a standard television system, the aspect ratio of an image remains the conventional 4:3.
As is known to those skilled in the art, if an image is to be displayed on a large screen of 100 inches or above, such as the projection screen of a projection display apparatus (hereinafter referred to as the "projector"), it is desirable to adopt a screen wider than a screen having the conventional 4:3 aspect ratio (for example, a screen having an aspect ratio of 16:9) if the visual characteristics of human beings are taken into account.
On the basis of the above-described concept, in the field of high-definition television systems or other similar systems which can handle high-quality images, a system has been proposed which employs an enlarged screen and which enables an image to be photographed and/or displayed at the 16:9 aspect ratio or another aspect ratio which is different from the conventional 4:3 aspect ratio.
However, in such a high-definition television system which greatly differs from the existing standard television system, to attain a wide screen, it is necessary to employ exclusive apparatuses for recording and reproduction, respectively. This arrangement compels users to pay great expenses.
If an image of different aspect ratio is to be recorded and/or reproduced by mean s of an apparatus conforming to the existing standard television system, only a portion of the effective screen of an image sensor or a reproducing apparatus is utilized and the number of effective pixels per image is reduced. This reduction in the number of effective pixels is undesirable in that the degradation of image quality is involved.
To cope with the above problems, an apparatus is proposed which utilizes a linear compression optical system (anamorphic lens) to achieve a wide screen while making the best use of a conventional apparatus without reducing the number of effective pixels. In such an apparatus, during photography, the aspect ratio of an image is optically converted by means of one anamorphic lens and the resultant image having a different aspect ratio is recorded. During reproduction, another anamorphic lens having substantially identical characteristics is employed to convert optically the different aspect ratio into the original aspect ratio, thereby reproducing the original image. For example, Japanese Laid-Open Patent Application No. Hei 2-170790 discloses a magnetic image-information recording and reproducing apparatus provided with a plurality of anamorphic lenses and arranged to record an image and a plurality of kinds of detection codes for discrimination between image compression ratios in a control track on a video tape which is a recording medium for recording of the image. During reproduction, an anamorphic lens used for recording is replaced with a different anamorphic lens on the basis of the detection code and the image is reproduced by means of the different anamorphic lens.
However, the ratio at which such an apparatus converts the aspect ratio of an image is fixed.
In other words, in the case of a system which records an image having an aspect ratio of 16:9 and reproduces it as a display image having the 16:9 aspect ratio by means of an apparatus capable of recording and reproducing an image having the conventional 4:3 aspect ratio, if an image having an aspect ratio of 2:1 is to be recorded and reproduced by means of such a system, it is necessary to replace a converting optical system exclusive for recording with that exclusive for reproduction. This replacement is extremely time-consuming.